• Journal of Aerospace System Engineering
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• v.18 no.1
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• pp.72-78
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• 2024

It is essential to coincide with moving target planet at future arrival changing point during space flight time in an interplanetary orbit design. Transition orbit elements can be obtained from traditional Lambert solutions by adjusting initial and final positions include flight time. Two-point boundary values of orbits can be selected in the design process. From this point of view, interplanetary orbits are infinite if they can be acquired from departure velocity without limit. However, appropriate and optimized procedures are needed to obtain an optimum interplanetary orbit to meet given conditions. The departure velocity is highly dependent on space launch vehicle's ability up to now. In this paper, algorithms of professor Howard Curtis at Embry-Riddle Aeronautical University were applied to obtain Lambert solution and orbit elements.

• Information and Communications Magazine
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• v.10 no.4
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• pp.53-62
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• 1993

정지궤도(Geo-Stationary Orbit)상의 통신위성의 정상운용 말미에 경제적 이유 또는 차세대 위성 발사지연등 기술적사유로 설계수명을 지난 후 경사궤도(Inclined Orbit)상의 위성 비정상운용을 개선하기 위하여 경사궤도의 개념, 도플러효과에 따른 지구국 설비 대책 및 INTELSAT 위성궤도 장기 운용계획 등을 조사 고찰한 것이다. 특히 경사궤도가 미치는 영향은 주파수, 안테나크기, 지구국 위도, 위성과 지구국과의 경도간격, 서비스의 디지틀과 애너로구등 다양한 요소를 수식화했다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.65-70
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• 2003

In this work variations of orbital parameters are first derived from the perturbation equations using difference equation method under Earth oblateness and atmospheric drag. A simple and effective scheme is proposed to compute the required delta v and fuel consumption to compensate for atmospheric drag. The scheme is applied to KOMPSAT example. And by means of numerical simulations we quantitatively analyze influences due to each perturbation source, i.e., nonspherical Earth, atmospheric drag, third body gravities (Sun, Moon), and solar radiation.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.165-166
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• 2014

위성의 전력 시스템 초기 설계를 위해 고려해야 하는 중요한 설계 요소에는 위성 운용 기간 동안의 전력 소모량 예측 및 전이궤도와 운용궤도에서의 태양 전지판과 배터리의 운용 개념 설계이다. 이를 토대로 태양 전지판에서 생성되는 전력의 정류 개념과 배터리 충전/방전 토폴로지를 구현해야 한다. 본 논문에서는 2.5KW급 정지궤도 위성의 전력 시스템 초기 설계를 위해 고려해야 하는 설계 요소들을 나열하고, 이들에 대한 전반적인 검토 사항을 기술한다.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.381-385
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• 1997

A long-term prediction algorithm of geostationary orbit was developed using the analytical method. The perturbation force models include geopotential upto fifth order and degree and luni-solar gravitation, and solar radiation pressure. All of the perturbation effects were analyzed by secular variations, short-period variations, and long-period variations for equinoctial elements such as the semi-major axis, eccentricity vector, inclination vector, and mean longitude of the satellite. Result of the analytical orbit propagator was compared with that of the cowell orbit propagator for the KOREASAT. The comparison indicated that the analytical solution could predict the semi-major axis with an accuracy of better than $pm35$ meters over a period of 3 month.

• Bulletin of the Korean Space Science Society
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• 1997.04a
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• pp.23.2-23
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• 1997

• Journal of Astronomy and Space Sciences
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• v.3 no.2
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• pp.93-102
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• 1986

For a geostationary satellite east-west station keeping maneuvers must control both the mean longitude and the orbit eccentricity simultaneously. The effect on the orbit eccentricity of maneuvers may be reprensented by a phse plane of $e_{c}$ verse $e_{s}$, since these eccentricity elements give the projection of the orbit center onto the equatorial plane in units of the semimajor axis. The evolution of the mean longitude and the orbit eccentricity are obtained.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.10
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• pp.40-50
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• 2003

The operational orbit evolution of the KOMPSAT-l over 3 years was analyzed. During LEOP, four orbit maneuvers were performed to obtain the optimized orbit and eight safe-hold modes happened. The effects of unpredictable occurrence of the safe-hold mode and the highest solar activity on the orbit evolution during the mission life were analyzed. The comparison of orbital elements between long-term predicted orbit and determined orbit from observed data was also performed. The operational orbit started from the optimized one was evolved within the boundary of the designed mission orbit except altitude and it was verified the sun-synchronous orbit was successfully maintained.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.23 no.2
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• pp.137-145
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• 2005

In this paper, we investigate the accuracy of various sensor models developed for linear pushbroom satellite images. We define the accuracy of a sensor model in two aspects: the accuracy of bundle adjustments and the accuracy of estimating exterior orientation parameters. The first accuracy has been analyzed and reported frequently whereas the second accuracy has somewhat been neglected. We argue that the second accuracy is as important as the first one. The second accuracy describes a model's ability to predict satellite orbit and attitude, which has many direct and indirect applications. Analysis was carried out on the traditional collinearity-based sensor models and orbit-based sensor models. Collinearity-based models were originally developed for aerial photos and modified for linear pushbroom-type satellite images. Orbit-based models have been used within satellite communities for satellite control and orbit determination. Models were tested with two Kompsat-1 EOC scenes and GPS-driven control points. Test results showed that orbit-based models produced better estimation of exterior orientation parameters while maintained comparable accuracy on bundle adjustments.

• Journal of the Korean Society for Railway
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• v.19 no.1
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• pp.67-76
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• 2016

The asphalt-concrete trackbed system has many advantages in terms of maintenance and economics. However, methods to investigate practical use corresponding to the development of the trackbed system must be developed. The primary objective of this study was to evaluate the dynamic performance of the asphalt system in accordance with both the elastic and viscoelastic material characteristics and design thickness of the asphalt trackbed. More specifically, in order to reduce the uncertainty error of the Finite Element(FE) model, a three-dimensional full scale FE model was developed and then the infinite foundation model was considered. Finally, to compare the condition of viscoelastic materials, performance evaluation of the asphalt-concrete trackbed system was used to deal with the dynamic amplification factors; numerical results using isotropic-elastic materials in the FE analysis are presented.